1. Field of the Invention
The present invention relates to an electronic-component (EC) mounting apparatus and particularly to the art of improving the durability of the EC mounting apparatus.
2. Related Art Statement
There is known an EC mounting apparatus which includes a movable EC mounting head for mounting an EC or ECs on an object such as a printed circuit board (PCB). The prior EC mounting apparatus includes (a) a frame member, (b) a movable member supported by the frame member such that the movable member is movable relative to the frame member, (c) a moving device which moves the movable member relative to the frame member, and (d) a mounting head which is provided on the movable member and mounts an electronic component (EC) on an object. The prior apparatus additionally includes a mounting-head moving device including an actuator for moving the mounting head relative to the movable member.
An example of the above EC mounting apparatus is disclosed in Japanese Patent Application laid open for inspection under Publication No. 2(1990)-69999. The disclosed EC mounting apparatus includes a rotary head which is supported by a frame member such that the head is rotatable about a vertical, axis line thereof. A plurality of EC mounting heads are provided along a circle whose center rides on the rotation axis line of the rotary head. Each of the EC mounting heads includes an EC suction nozzle for holding an EC by vacuum. The EC suction nozzle is supported by a support member of the EC mounting head such that the suction nozzle is directed downward and is rotatable about an axis line thereof. On the rotary head, there are provided a plurality of rotating devices for the plurality of EC mounting heads, respectively. Each rotating device has a drive source in the form of an electric motor and rotates the EC suction nozzle about the axis line thereof. Meanwhile, on the side of the frame member, there are provided an EC supplying section where ECs are supplied to the side of the rotary head, a EC-holding-error detecting section where error of EC holding of the suction nozzle is detected, and an EC mounting section where ECs are mounted on a PCB.
As the rotary head is rotated, each of the EC mounting heads is sequentially moved to the EC supplying section, EC-holding-error detecting section, and EC mounting section one after another in the order of description. Thus, an EC is held by an EC mounting head, error of holding of the EC is detected, and the EC is mounted on a PCB. At the EC-holding-error detecting station, positional errors, .delta.x, .delta.y, of the EC held by each EC suction nozzle are calculated in a horizontal X-Y coordinate or plane, and an angular error, .delta..theta., of the EC is calculated around the axis line of the suction nozzle. During a time duration when the EC mounting head is moved from the EC-holding-error detecting station to the EC mounting station, the EC suction nozzle is rotated to correct the angular error .delta..theta. of the EC held thereby.
In the case where the electric motors are provided on the rotatable rotary head as described above, it is required that electric energy be supplied from a power source provided on the frame member, to the electric motors on the rotary head, irrespective of the current rotational phase of the rotary head. The above-identified patent document fails to specify how to supply the electric energy from the side of the frame member to the side of the rotary head. Generally, however, slip rings are used. For example, a metal ring as a slip ring is attached to the rotary head and an electrically conductive brush fixed to the frame member is contacted with the metal ring, so that electric energy is supplied through the brush and ring. In this case, the same number of slip rings as that of the electric motors are employed, so that the electric energy is supplied to each of the electric motors.
Since, however, the slip rings are used such that the electric energy is supplied through the brush contacted with the metal rings that rotate together with the rotary head, the EC mounting apparatus suffer from low durability and low life expectancy.
The above problems also occur to a different EC mounting apparatus wherein a movable member is reciprocated along a straight or curved line. In the second apparatus, too, if the movable member is provided with an electric actuator that is operable on electric energy, it is also required that the electric energy be supplied from the side of a frame member to the side of the movable member, irrespective of the current relative-positional relationship between the two members.